1. Field of the Invention
The application of various sensor technologies to vehicles in motion such as aircraft, air vehicles and space vehicles as well as to other surfaces exposes the sensors to vibrations. These vibrations are defined as the continuous and non-continuous, periodic and non-periodic accelerations which result in changes in displacement about the fixed axes of the sensors. Such vibration when coupled to the sensor may cause undesirable effects to the information provided by the sensor, as by masking and altering the signal therefrom. In the case of a sensor which oscillates at a frequency responsive to a selected parameter to be sensed, vibration from such external surface may alter or fully obscure the oscillation responsive to the selected parameter. Such vibrations may be linear and/or rotational. Where the sensor is sensitive to certain of such vibrations, the sensor must be isolated from those vibrations in order to obtain intelligible information therefrom. A vibrating sensor member, such as used in a vibrating wire or beam sensor, for example, may be sensitive to all external linear vibrations and to external rotational vibrations perpendicular to the longitudinal plane of such vibrating member.
2. Prior Art
In the prior art, elastomeric material such as rubber in various forms are known vibration isolators. Similarly, it is known that placement of elastomers about the periphery of a sensor housing having a vibration sensitive sensor therein reduces the effects of certain vibrations. For example, in the prior art mounting shown in FIG. 1, rubber columns 4 are mounted on the front and rear facing sides of the housing, these columns are then rigidly affixed to a selected surface to support the housing in a desired position. When a linear vibration acts on the surface and is transmitted to the housing through the elastomeric material along the X axis of the housing, two columns are in compression and two columns are in tension. However, a vibration acting force along the Y axis or the Z axis causes all four columns to be in shear. Due to the very nature of the elastomer, it tpyically provides a stiffer response in compression (or tension) than in shear. Additional columns only add cost and provide further coupling means for the unwanted vibrations to the housing. Linear vibrations along the Y and Z axes are isolated by the system of FIG. 1, but rotational vibrations caused by the movements in direction along the stiff linear axis X provides additional problems as such linear vibrations about X can be converted to moments causing rotational vibration C about axis Z. The structure of FIG. 1 is effective only partially against rotational vibrations C about the Z axis, as the four columns are in a combination of shear and compression or tension in response to such vibration. As fully explained herein, the result of this invention is that improved isolation from such rotational vibration is obtained when all four columns are primarily in compression or tension. The center of gravity of the housing and the elastic center of the isolation system should be concentric, as otherwise the eccentricity of these centers together with the linear accelerations provide the moment arm for forces derived from such linear vibrations which are then converted to rotational vibrations which are also are unwanted.